Oil Stiction in Fast Switching Annular Seat Valves for Digital Displacement Fluid Power Machines

Digital Displacement (DD) fluid power machines utilizes electronically controlled seat valves connected to pressure chambers to obtain variable displacement with high operational efficiency and high bandwidth. To achieve high efficiency, fast valve switching is essential and all aspects related to the dynamic behaviour of the seat valves must be considered to optimize the machine efficiency. A significant effect influencing the valves switching performance is the presence of oil stiction when separating the contact surfaces in valve opening movement. This oil stiction force is limited by cavitation for low pressure levels, e.g. valves connected to the low pressure manifold, however for valves operated at higher pressure levels, the oil stiction force is dominating when the separating surfaces are close to contact. This paper presents an analytic solution to the oil stiction force for annular seat valves suitable for DD applications based on the Reynolds equation and considers contact surface curvature and attack angle. A dynamic cavitation zone is included in the stiction model, and cavitation is found to be present even for seat valves surrounded by high pressure levels.

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Analysis of Requirements for Valve Accuracy and Repeatability in High Efficiency Digital Displacement Motors

BATH/ASME 2018 Symposium on Fluid Power and Motion Control ◽

10.1115/fpmc2018-8908 ◽

2018 ◽

Author(s):

Sondre Nordås ◽

Morten K. Ebbesen ◽

Torben O. Andersen

Keyword(s):

High Pressure ◽

High Efficiency ◽

Valve Timing ◽

Rotary Valve ◽

Fast Switching ◽

Flow Capacity ◽

Constant Friction ◽

Variable Displacement ◽

Piston Stroke ◽

Accuracy And Repeatability

Traditional variable displacement piston machines achieve high efficiency when operating at high displacements, but struggle with poor efficiency at low displacements. The pistons are connected to high pressure and low pressure in conjunction with the output shaft position and the displacement is changed by changing the piston stroke, resulting in almost constant friction, leakage, and compressibility losses independent of displacement. In digital displacement machines, the rotary valve is replaced by two fast switching on/off valves connected to every cylinder. By controlling the fast switching on/off valves, the cylinders can be controlled individually and friction, leakage and compressibility losses can be minimized resulting in high efficiency even at low displacements. Previous studies have shown that high efficiency digital displacement machines require fast switching valves with high flow capacity and optimal valve timing strategy. When the digital displacement motor is to start, stop or be controlled at low speeds, the on/off valves must be able to open against high pressure difference. When opening the valves actively, the valve timing has to be conducted properly to minimize valve throttling losses and flow and pressure peaks. First, this paper shortly describes a previously developed method to estimate valve characteristics like transition time and flow capacity for a digital displacement machine. Then the paper presents a novel method of describing the required valve accuracy and repeatability to keep the valve throttling losses low and machine efficiency high.

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RHELP (Regenerative High Efficiency Low Pressure) Air Purification System

10.21236/ada511241 ◽

2009 ◽

Author(s):

Chang-Yu Wu ◽

Brian Damit ◽

Qi Zhang ◽

Myung-Heui Woo ◽

Wolfgang Sigmund ◽

...

Keyword(s):

High Efficiency ◽

Low Pressure ◽

Air Purification ◽

Purification System

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Design Method for Fast Switching Seat Valves for Digital Displacement® Machines

8th FPNI Ph.D Symposium on Fluid Power ◽

10.1115/fpni2014-7852 ◽

2014 ◽

Cited By ~ 4

Author(s):

Daniel B. Roemer ◽

Per Johansen ◽

Henrik C. Pedersen ◽

Torben O. Andersen

Keyword(s):

Pressure Loss ◽

Design Method ◽

Thermal Dissipation ◽

Valve Design ◽

Stroke Length ◽

Efficient Operation ◽

Fast Switching ◽

Switching Times ◽

High Bandwidth ◽

Electro Magnetic

Digital Displacement® (DD) machines are upcoming technology where the displacement of each pressure chamber is controlled electronically by use of two fast switching seat valves. The effective displacement and operation type (pumping/motoring) may be controlled by manipulating the seat valves corresponding to the piston movement, which has been shown to facilitate superior part load efficiency combined with high bandwidth compared to traditional displacement machines. However, DD machines need fast switching on-off valves with low pressure loss for efficient operation, especially in fast rotating operation, where switching times must be performed within a few milliseconds. These valve requirements make a simulation based design approach essential, where mechanical strength, thermal dissipation, fluid dynamics and electro-magnetic dynamics must be taken into account. In this paper a complete design method for DD seat valves are presented, taking into account the significant aspects related to obtaining efficient DD valves with basis in a given DD machine specifications. The seat area is minimized and the stroke length is minimized to obtain fast switching times while considering the pressure loss of the valves. A coupled optimization is finally conducted to optimize the electro-magnetic actuator, leading to a valve design based on the chosen valve topology. The design method is applied to an example DD machine and the resulting valve design fulfilling the requirements is presented.

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Development of a New Design Method for High Efficiency Swept Low Pressure Axial Fans With Small Hub/Tip Ratio

Volume 1A: Aircraft Engine; Fans and Blowers ◽

10.1115/gt2014-25932 ◽

2014 ◽

Cited By ~ 1

Author(s):

Thore Bastian Lindemann ◽

Jens Friedrichs ◽

Udo Stark

Keyword(s):

High Efficiency ◽

Design Method ◽

Tangential Velocity ◽

Pressure Rise ◽

Low Pressure ◽

Aerodynamic Performance ◽

Low Noise ◽

Angle Distribution ◽

Sweep Angle ◽

Reduced Pressure

For a competitive low pressure axial fan design low noise emission is as important as high efficiency. In this paper a new design method for low pressure fans with a small hub to tip ratio including blade sweep is introduced and discussed based on experimental investigations. Basis is an empirical axial and tangential velocity distribution at the rotor outlet combined with a distinctive sweep angle distribution along the stacking line. Several fans were designed, built and tested in order to analyze the aerodynamic as well as the aeroacoustic behavior. For the aerodynamic performance particular attention was paid to compensate the influence of reduced pressure rise and efficiency due to increasing blade sweep. This was achieved by a method of increasing the blade chord depending on the local sweep angle which is based on single airfoil data. The tested fans without this compensation revealed a significant noise reduction effect of up to approx. 6 dB(A) for a tip sweep angle of 64° which was accompanied by an unsatisfactory effect of reduced overall aerodynamic performance. The second group of fans did not only confirm the method of the aerodynamic compensation by a nearly unchanged pressure rise and efficiency characteristic but also revealed an increased aeroacoustic benefit of in average 9.5 dB(A) compared to the unswept version. Beside the overall characteristics the individual differences between the designs are also discussed using results of wall pressure measurements which show some significant changes of the blade tip flow structure.

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Development of composite filters with high efficiency, low pressure drop, and high holding capacity PM2.5 filtration

Separation and Purification Technology ◽

10.1016/j.seppur.2018.11.068 ◽

2019 ◽

Vol 212 ◽

pp. 699-708 ◽

Cited By ~ 15

Author(s):

De-Qiang Chang ◽

Chi-Yu Tien ◽

Chien-Yuan Peng ◽

Min Tang ◽

Sheng-Chieh Chen

Keyword(s):

Pressure Drop ◽

High Efficiency ◽

Low Pressure

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Ripple cancellation technique applied to a synchronous buck converter to achieve very high bandwidth and very high efficiency envelope amplifier

2013 Twenty-Eighth Annual IEEE Applied Power Electronics Conference and Exposition (APEC) ◽

10.1109/apec.2013.6520580 ◽

2013 ◽

Cited By ~ 5

Author(s):

D. Diaz ◽

O. Garcia ◽

J.A. Oliver ◽

P. Alou ◽

J.A. Cobos

Keyword(s):

High Efficiency ◽

Buck Converter ◽

High Bandwidth ◽

Ripple Cancellation ◽

Very High

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Hipernetch: High-Performance FPGA Network Switch

ACM Transactions on Reconfigurable Technology and Systems ◽

10.1145/3477054 ◽

2022 ◽

Vol 15 (1) ◽

pp. 1-31

Author(s):

Philippos Papaphilippou ◽

Jiuxi Meng ◽

Nadeen Gebara ◽

Wayne Luk

Keyword(s):

High Frequency ◽

High Performance ◽

Data Centers ◽

Round Robin ◽

Switching Performance ◽

Wide Range ◽

Crossbar Switches ◽

High Bandwidth ◽

Network Switch ◽

Network Switches

We present Hipernetch, a novel FPGA-based design for performing high-bandwidth network switching. FPGAs have recently become more popular in data centers due to their promising capabilities for a wide range of applications. With the recent surge in transceiver bandwidth, they could further benefit the implementation and refinement of network switches used in data centers. Hipernetch replaces the crossbar with a “combined parallel round-robin arbiter”. Unlike a crossbar, the combined parallel round-robin arbiter is easy to pipeline, and does not require centralised iterative scheduling algorithms that try to fit too many steps in a single or a few FPGA cycles. The result is a network switch implementation on FPGAs operating at a high frequency and with a low port-to-port latency. Our proposed Hipernetch architecture additionally provides a competitive switching performance approaching output-queued crossbar switches. Our implemented Hipernetch designs exhibit a throughput that exceeds 100 Gbps per port for switches of up to 16 ports, reaching an aggregate throughput of around 1.7 Tbps.

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